John Sayers' Recording Studio Design Forum Archive

Hello All,
Back again with questions I shouldn't be needing to ask!
Am at a stage of my construction where I am facing some imminent decisions that by rights I should have addressed ealier in my planning stage but I am where I am and for that am feeling pretty self-condemning!
following on from recent posts I need advice on a couple of key issues.

Floor will soon go down, currently there is a concrete slab with DPM ontop. next will go 50mm Celotex then underlay and laminate flooring ontop.
befor getting to next stage I have discussed wth builder (not studio build specialist) about addressing the 25mm gap between the concrete base and the walls (2x15mm PB). He seems to think this gap doesn't need caulking but to me alarm bells are ringing loud!

According to my research on this and other forums it needs backer rods pushed into all gaps then caulked thoroughly to fill the gap fully, some gaps may not fit backer rods so just fill with caulk in these cases?

Am I correct?

I assume acoustic caulk is best but any other suitable alternative suggestions welcome.

Other issue ringing 120db alarm bells is the penetration of the electrical armoured cable which will bring power to the structure.

The original feeding in of the cable has not been done correctly as far as I can see. cable was brought in via external trench then into the cavity (now filled with 100mm Rockwool) between the external OSB layer. It was brough in before the PB layers were put up and not line of sight penetration (came from below then up to penetrate PB at higher level) but was not put in a conduit so therefore no decoupling of conduit sections.
pic shows a massive hole with cable penetration showing, also visible through the hole under the plasterboard is the top of a resilient channel. Have included pics and a simple sketch (PB fixed to studs but these not shown in sketch)

Discussing with electrician how to seal this to the best degree possible prior to installing service panel at that location I outlined that the cable should be threaded into a conduit going down as far as possible then conduit stuffed with rockwool (down into conduit as far as possible) then sealed with caulk as far into conduit mouth as possible and where it appears at interior surface. He says he can't do that!

I am aware that this is a solution far from ideal but is it the best possible remedy to what I see as an appalling situation?

Also notice that inside the hole the 2 flanges of the visible RC have plasterboard dust/powder in between which will have to be got out to avoid short-circuiting the isolation provided by the RC.

A also assuming the empty space now visible behin dthe PB needs to stuffed full of RW?

Any advice would be very valued
thank you
Jose

reviewing my last submitted post it seems that some pics were not appearing so here they are
Jose

Floor will soon go down, currently there is a concrete slab with DPM ontop. next will go 50mm Celotex then underlay and laminate flooring ontop.

Ummmm... Nope! You cannot lay laminate on top of a soft and spongy layer, like Celotex! You need a sub-floor. Lay at least one layer of at last 15mm OSB, MDF or plywood. Preferably two layers, and preferably 19mm. If you lay laminate flooring directly on "soft and spongy", it will crack, and also you will have no isolation... Leave a gap around the edge of the plywood/MDF/whatever, so that it does not touch the walls. Fill with backer rod and caulk.

addressing the 25mm gap between the concrete base and the walls

I don't understand: Why would there be any gap at all between the walls and the floor¡???? Are the walls somehow levitating above the floor???? How on earth are you managing to build your walls such that they don't reach the floor?????

Please post some photos of this "gap".... I'm intrigued!

the penetration of the electrical armoured cable which will bring power to the structure. .... then into the cavity (now filled with 100mm Rockwool) between the external OSB layer.

Between that and what? Your sentence says that the cable comes up into the wall cavity between the OSB and something else, but you didn't way what the "something else" is.

but was not put in a conduit so therefore no decoupling of conduit sections.

It is an armored cable: therefore it is not flexible. It is quite solid and rigid, so trying to decouple if with conduit will not help a lot. If I'm understanding correctly, your best option is to get the electrician to form a large "loop" of cable that is hung from the outer wall framing at one end (hopefully with a soft rubber-covered attachment of some type) and hung from the inner-leaf at the other end, with just the looped part in between not touching either leaf. Then bring the near end in through the drywall directly into the distribution panel, and seal that penetration very well.

reviewing my last submitted post it seems that some pics were not appearing so here they are

IT looks like you are posting them as TIF files. The forum apparently does not accept TIF files. Convert them to JPG and post them again.

- Stuart -

Hi Stuart,
thank you very much for your reply. Yes! I did make an error with my floor build up details, I missed out the layer of OSB! layers would be as follows.

CONCRETE BASE (WITH dpm)
50MM CELOTEX
18MM OSB
UNDERLAY
LAMINATE FLOORING.

have re-attached pics of floor/wall gap to clarify. PB was fixed to the RCs but I (mistakenly?) instructed builder to leave this gap between bottom of PB and floor in order for vibration to not be transmitted from floor to walls and vica versa with the intention of caulking this gap at this stage. I really though this is how it should be done. Have I done this wrong?

As this is the way it is today should I install backer rods and caulk this gap then add floor layers from then?
As you can see currently the only thing between the inside and outside at floor level is 18mm of OSB. This is not isolated at all as you say .

Regarding cable penetration- cable comes in at a low level via trench into the cavity between outer OSB layer and the 2 layers of PB which are fixed to the RCs, these constitute the inner leaf. This cavity contains 100mm of Rockwool.

the wall are now closed and sealed meaning I would not be able to employ your suggestion of hanging cable between OSB and PB. As you can see from the pic the cable is where it is and I cannot access the space between outer and inner leaves so I think my task is to ensure that the hole shown in the pic is sealed as throughly as possible.

That being the case what would be the best way to seal that hole and cavity that already contain the armoured cable? As you can see there is a lot of RW now missing from the cavity in that place so guessing that should be plugged with RW?

Your advice is much appreciated Stuart.
Jose